Selecting apparatus for telephone systems.



0. E. NICHOLAS.

' SELECTING APPARATUS FOR TELEPHONE SYSTEMS.

APPLICATION FILED DEO.18, 1901.

944,460, Patented Dec. 28, 1909.

' 2 SHEETS-SHEET 1.

I nventor.

witneeu' torney C. E. N IGHQLAS.

SELECTING APPARATUS FOR TELEPHONE SYSTEMS.

APPLICATION FILED DEC. 18, 1901.

, Patented Dec. 28, 1909.

2 SHEETS-SHEET 2.

' {1 07 llllllllill [N M 6mm r O t n .e v n I Witnesses- UNTTED STATESPATENT FFQ 1 CHARLES E. NICHOLAS, OF COLUMBUS, OHIO, ASSIGNOR TONICHOLAS TELEPHONE SELECTOR COMPANY, OF ROCHESTER, NEW YORK, ACORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Dec. 28, 1909.

Application Med December 18, 1901. Serial No. 86,372.

To all whom it may concern:

Be it known that 1, CHARLES E. NICHOLAS, of Columbus, in the county ofFranklin and State of Ohio, have invented certain new and usefulImprovements in Selecting Apparatus for Telephone Systems; and I dohereby declare the following to be a full, clear, and exact descriptionof the same, reference being had to the accompanying drawings, forming apart of this specification, and to the reference characters markedthereon.

My present invention relates to telephony and particularly to thatbranch known as multiple circuits, in which a plurality of telephoneinstruments are connected to a single circuit, and it has for its objectto provide a selecting device operating in connection with each of theinstruments on said circuit, whereby when one of the instruments is inoperation the others will be disconnected from the circuit and in whichall of the instruments may be restored to their normal position inconnection with said circuit after each operation.

My invention has for its further object to provide means by whichcommunication may be had between any two instruments on a single circuitand the remaining instruments disconnected therefrom.

To these and other ends, the invention consists in certain improvementsin construction and combination of parts, all as will be hereinafterfully described, the novel features being pointed out in the claims atthe end of this specification.

In the drawings: Figure 1, is a front elevation of a selecting devicefor a multiple, telephone system constructed in accordancewith myinvention, shown with the front of the casing removed. Fig. 2, is across sectional view thereof on the line aa of F ig. 1; and Fig. 3, is arear view taken on the line b:Z2 of Fig. 2. Fig. at, is a diagrammaticview of a multiple telephone system of three instruments. lar viewshowing in detail the contact points of the several selectors connectedto said instruments.

Similar reference numerals in the several figures indicate similarparts.

In illustrating my device I have shown it Fig. 5, is a simiin connectionwith mechanism employed for operating the usual form of a metallictelephone circuit, a number of which are controlled from a centralstation.

The main wires forming the circuit are in dicated by 1 and 2 which leadto the line bat tery 3 at the central station and at which point theymay be connected in the usual or any preferred manner to the usualsignaling devices, as will be understood, and in place of the battery 3a dynamo may be employed to furnish the requisite continuous current, ifdesired.

8 indicates a switch arranged in the main circuit wires for the purposeof disconnecting the batteries 3 from the circuit when the latter is atrest.

The telephone instruments I have employed in connection with my deviceare of the usual type embodying a transmitter 10 and a receiver 11arranged in the usual manner between the line wires 1 and 2 terminatingin the binding posts 12 and 13 on the selector and also connected tosaid posts is a magneto generator 16. Each of the instruments connectedto the main circuit constitutes a sub-circuit complete in itself, and itwill be understood that any desired kind of instrument may be employedas well as the telephone instrument which I have se-.

lected to illustrate the operation of my device.

The selecting device, the detail construction of which is shown in Figs.1, 2, and 3, is mounted in a small cabinet 18 having the back 1 9 andthe door or front 20, and it consists generally of a support 21 ofinsulated material having a series of contacts thereon with whichengages a contact arm or switch and also provided with suitable meansfor operating the latter, as will be further described.

23 indicates a frame or' support from which are downwardly extendingears or lugs 24 carrying adjustable trunnion screws 25 and between thelatter is pivoted a beam arm 26 connecting the coils of an electromagnetwhich extend parallel with each other and are indicated by 27 and 28.Arranged between and slightly below the ends of the cores of the magnetis the end of a permanent or bar magnet 29, whereby one rection of theflow of current through the coils, as will be understood, causing thebeam 26 to swing on the bearing to the positions shown in full anddotted lines in Fig. 3. Rigidly mounted on the frame 23 is a post 30, towhich is pivoted a plate 31 provided in its outer edge with a series ofnotches or teeth 32 and engaging therewith is a pawl 33 attached to thebeam or arm 26 and adapted when the latter is operated in one direction011 its pivot to move the plate 31 upwardly a distance equal to thespace of one tooth, and when the beam is operated to the limit of itsmovement in the opposite direction to be carried out of engagement withthe plate. In order to lock the plate in adjusted position I provide apawl or lock member 34, pivoted to the frame at 35, having an arm 36provided with a finger or eX- tension 37 extending downwardlyand'adapted to cooperate with one end of the beam or arm 26 to releasethe pawl, simultaneously with the disengagement of the pawl 33, to

permit the plate to return to its original position. Attached to therear of the plate 31 V is a contact finger 40 adapted, when the plate isin its normal or lower position, to engage a contact pomt 41 and when adusted to a predetermined point to engage a second contact point 42, saidpoints being connected by a wire 43 and also connected by a wire 44 withthe binding post 13.

The contacts 41 are located in the same position in each of theselectors and for 'convenience will be termed home points, and when thedevices are in their normal position the contact fingers 40 engagetherewith. The points 42 however are arranged in a different position ineach selector, being separated from the home points bya number of suchspaces traversed by the contact arm as the plate is actuated, a tooth ata time, such spaces corresponding to a predetermined number given to anyparticular instrument.

This will be readily understood by reference to Fig. 5 in which a seriesof selecting instruments are indicated by I, II, III. In the first, thecontact point 42 is separated from the home point by a single space, thesecond separated two spaces and the third three spaces. The selector forany subsequent instruments that might be added to the circuit would besimilarly arranged by increasing the distances between the contacts byone step for each of said instruments. From the above it will be seenthat by arranging all the selectors for simultaneous operation andoperating them all the same number of times, any of the local signalingand telephone circuits maybe connected to the main circuit while theremainder are disconnected therefrom. In Fig. 5, the plates 31 have beenactuated three times,

carrying the contact arms 40 to the third position, where said arm ofthe third selector, engages its contact 42, the plates of the selectorsconnected to the instruments I and II having been actuatedcorrespondingly, their contact fingers are out of engagement with theirrespective contacts 42.' When in this position it is impossible foreither of the signal or telephone instruments at stations I and II to beused until restored to the line,

as will be further described. v

The operation of the selectors is controlled from the central station bymeans of the spring operated switch 8 which normally stands in the openposition, as shown in Fig.

4. The coils of the electro-magnet are pawl 33 operating the plate 31the distance of one of the teeth 32 when it is locked bythe pawl 34.'lVhile the current passes over the circuit continuously, the magnetsremain in i this position, but when the current is interrupted byopening the switch, the electromagnets immediately assumetheir normalposition, as shown in Fig. 1, and subsequent positive impulses operatingthe magnets as before, will cause the selectors'to be operated. asuflicient number of times to bring the desired instrument into thecircuit through its individual contact 42. electro-magnets beingentirely below their pivotal center is liable. to cause them to swingunduly when the current is broken.

and to arrest this movement I provide a friction brake in the form ofalight leaf spring 45, supported upon a post 46 and secured by a screw47 and bearing against small bars 48 forming bearing surfaces upon thesides of the magnet coils. The screw 47 being arranged between thelatter may be regulated to adjust the tension of the spring equally uponboth of them.

As the electro-magnets are polarized, or their coils Wound in differentdirections, they are operated in one direction by a positive current, toactuate the plate 31, and in the opposite direction by a negativecurrent, to disengage the actuating and locking pawls, to permit thereturn of the selector plate to its normal position, as shown in .dottedlines in Fig. 3. This is accomplished by means of a pole changer 80arranged at the central station connected to the circuit conductors 1and 2 and adapted to engage thecontacts 81 and 82 of the wires 102 and201 respectively,

The weight of the j.

said Wires leading from the sides of the battery 3 opposite to those towhich the wires 1 and 2 are connected.

The selector is adapted to control the instrument or local circuit andto accomplish this, one of said circuit conductors 2 passes directlythrough the device and for convenience in construction, said conductoris provided in each selector, terminating in the binding posts 12 and120 arranged at the upper and lower sides respectively of the cabinet.The other circuit conductor 1" enters and leaves the selector, by thebinding posts 13 and 130 respectively, and intermediate the latter arearranged the contacts 41 and 42 which form dual terminals for one end ofsaid conductor and to which it is con- 40 from whichleads a conductor11" connected to the main circuit at the post 130. The circuit throughthe coils forming the ends 27 and 28 of the electro-magnets is connectedby the wires or conductors 270 and 280 to the conductors 2 and 11 but onaccount of the resistance afforded by coils of the electro-magnet thereis no short circuiting through the shunt, thus formed, which willinterfere with the operation of the instrument.

In order that the signal device or bell shall be operated only on theinstrument it is desired to bring into the circuit, I connect the coilsof said bell, indicated by to the circuit by the conductors 1 and 2, oneof which, the former, as shown, terminates in a contact 51 arrangedadjacent the contact 42 and adapted to be engaged by the finger 40 whenthe latter engages the contact 42 and to be bridged into the main linethrough the conductors 11 and 1". And while I have not shown thesignaling device arranged in the selector cabinet it may be locatedtherein, or the conductor 1 may be connected to a binding post C and thecircuit completed from thereon, as usual.

Intercommunication may be had between two or more instruments on thesame main circuit while the selectors connected to the remaininginstruments will cause the latter to be disconnected, by arranging inthe conductor 1 of each station a circuit-breaking switch and in shunttherewith a high resistance for continuous currents preferably in theform of a condenser 56. The latter prevents the passage of a continuouscurrent sufficiently strong to operate the electro-magnet or the bell 50but permits the passage of speaking or undulatory or pulsatory currentby which speech may be transmitted. hen, therefore, it is desired toconnect two instruments on the same line, the switch of the callingsubscriber is opened by him and the remaining selectors operated by thecentral operator, opening and closing switch-8 the number of timesrequired to connect the desired instrument through its contact 42 andfinger 40, when the switch may be closed, the finger 40 of this selectorbeing in contact with the home point 41. The condenser 56 might bedispensed with, but as speech may be transmitted through it, theoperator or subscriber is informed by the reply of the person called orby the central operator, of the proper time to restore his instrument tothe line by closing the switch. By reference to Fig. 4 it will be seenthat intercommunication may be had. between instruments I and III, inthe above manner, if the selecting device connected to the former isdisconnected from the circuit by opening the switch 55, and the centraloperator actuates the selectors on instruments II and III, three times,thereby closing the circuit to the latter through its contact 42,leaving the instrument II off the line, operates the calling signal, aswill be described, of station III, and then by closing the switch atstation I the first instrument is connected to the circuit with itsselector parts in their normal position. The operation may be reversed,as will be understood.

To provide a means whereby a person can readily determine whether aparticular telephone instrument is connected to or is off the circuit, Iarrange an aperture 60 in the front or door 20 opposite the plate 81 andon the latter are provided two colored or otherwise distinguishableindicating spots 61 and 62, the former being visible through theaperture when the plate is in its normal position, and the latter whenthe selector has been operated to bring its contact finger 40 intoengagement with the contact 42.

The operation of the device will be readily understood. hen in thenormal position all of the selectors are in the position shown in fulllines in Figs. 1 and 4, with their contact fingers 40 engaging thecontacts 41 and the respective telephone instruments operating inconnection therewith are connected to the circuit wires 1 and 2 throughthe conductors 1, 44, wire 43, contact 41, arms 40, and conductor 11,and conductors 2 and 2 the local telephone instruments being in circuitas usual, controlled by the usual receiver switch 111, these parts beingshown conventionally. To connect any particular telephone, forillustration say instrument III,

the operator closes the switch 8 three times, causing electric impulsesof one polarity to operate the electro-magnets three successive times inthe same direction.

wardly until the arm on selector III com- I.

pletes the circuit to its respective instrument v The impulses operatingthe coils 27 toward the permanent through the contact 42. At the sametime the contact finger engages the contact 51, completing the circuitthrough the signaling device or hell 50 of this particular instrumentpermitting it to be operated in the usual manner. The calling circuitmay be operated by what is termed central energy. and I have shown analternating current generator 4: having the wires terminating in thecontacts 5 and 6 which may be connected with the circuit wires 1 and 2by means of a switch 7. When the latter is moved into engagement withthe contacts 5 and 6 only the bell 50 of the selected instrument will beoperated. The switch 8 after being operated the desired number of timesis permitted to remain in the open position, disconnecting the linewires 1 and 2 from the battery 3, which allow the coils 27 and 28 andthe pawl 33 carried thereon to gravitate to their normal position, shownin Fig. 1. The current subsequently supplied to the main line to ringthe bells 50 is obtained "from the alternating current generator 4 whenthe switch 7, at the central station is moved into engagement with thecontacts 5 and 6. This current entering the coils 27 and 28 causes themto be charged alternately with positive and negative i1npulses ofcurrent which change too rapidly to allow either coil to be attractedtoward the permanent magnet 29 with suflicient force to overcome theinertia of their combined weight on their pivotal points or trunnions25. The several instruments are restored to the main circuit,simultaneously, by means of the pole changer 80, which, when engagedwith the contacts 81 and 82, causes the coils 28 to be attracted towardthe permanent magnets 29, This movement throws the pawls 33 out of thepath of the teeth 32 and the beam arms 26 engaging the tripping fingers37 will move the locking members or parts 34: out of engagement withsaid teeth, releasing the plates 31 and permitting them to return totheir normal position, carrying the arms l0 into engagement with thehome contact points 4L1 when all of the instruments will be connected tothe circuit, as before described.

The device which I have described enables me to provide a system inwhich a plurality of telephone instruments may be arranged upon a singlecircuit and any desired one selected without the necessity of employingeither a grounded connection or neutral conductor, thereby removing thepossibility of disturbances in any of the instruments from local causes.While I have confined the description of the operation of my device toits employment in connection with single telephones it will beunderstood that it may also be used to connect supplemental stationcircuits with a main central station circuit, and further while theselec tor is particularly adapted for telephone systems it may be usedequally well in c011- nection with other forms of instruments, theoperation of which it may be desirable to control from a single pointorstation.

The construction I have described may be varied by those skilled in theart without departing from the spirit of my invention and I do notdesire to be confined to the precise arrangement of the parts shown.

I claim as my invention:

1. The combination with a main circuit, a continuous current generator,an alternating current generator either of which is adapted to beconnected to the main circuit and a plurality of local circuits eachembodying a signaling instrument responsive to alternating currentsonly, and each provided with a stationary contact, of a plurality ofselectors one for each local'circuit, each embodying a movably supportedpolarized electro-magnetic coil arranged in the main circuit, a movableswitch arm adapted to cooperate with said contact, a member operated bythe movement otthe coil for adjusting the arm when it is moved in onedirection by successive impulses of continuous current of one polarity,the contacts of dif ferent local circuits being arranged at differentdistances from a neutral or normal position, a retaining device for themember released by the movement of the coil in a different directionwhen acted upon by currents of opposite polarity.

2. The combination with a main circuit, a continuous current generator,an alternating current generator adapted to be connected to the maincircuit and a plurality of local circuits each embodying a signalinginstrument responding to alternating currents, of

a plurality of selectors one'for each local circuit each embodying apolarized electromagnet arranged with its coils in the main circuitembodying a movable part moving in difi'erent directions when energizedby continuous electrical impulses of different polarity, a progressivelymovable member adapted to engage the contact, a pawl actuated by saidpart and cooperating with the member when the current in the magnet isof one polarity, contacts controlled thereby connecting the signalingdevice to the main circuit, the contacts of different local circuitsbeing arranged at dilierent distances from a neutral. or normal positionand a retaining device for each member adapted to be released by thearmature when the current in the magnet is of difterent polarity.

3. The combination with a main circuit, a 7

movable coil, an arm actuated thereby and cooperating with the switch tomove it into engagement with the retaining means to break the circuitwhen said coil is energized by currents of one polarity, said coiloperating to actuate said means to release the switch when energized bycurrents of a difi'erent polarity.

4:. The combination with a main circuit, a generator and a localtelephone circuit connected thereto, a gravity operated switch in thelocal circuit for breaking it and a retaining device cooperatingtherewith to hold the switch in operated position, of a polarizedelectromagnetic operating device comprising a movable coil, an armactuated thereby and cooperating with the switch to move it intoengagement with the retaining device to break the circuit when said coilis operated in one direction by currents of one polarity, said coiloperating it to release the switch when moved in the opposite directionby currents of a different polarity.

5. The combination with a main circuit, a continuous currentgeneratorand an alternating currentgenerator either of which is adapted to beconnected to the main circuit, of a plurality of stations, each having asig naling device responding to one kind of current arrangedin a circuithaving a con tact, a selecting device for each station em bodying aprogressively movable member, a retaining device therefor, a pivotedelectromagnet having a polarized armature and arranged in the maincircuit an arm actuated thereby and cooperating with said member tooperate it by successive. continuous current impulses of one polarity,into engagement with its respective contact, to connect the signalingdevice to the main circuit, said magnet being adapted to cooperate withand release the retaining device when acted upon by a continuous currentof opposite polarity.

6. The combination with the main circuit, a plurality of stat-ions eachhaving a local telephone circuit and a local signal circuit, a contactin each circuit, of a plurality of electro-magnetic selecting devicesone for each station and each embodying a polarized magnet in the maincircuit having a movable part responding differently to currents ofopposite polarity, a progressively movable member cooperating wlth saidcontacts and an arm cooperating with the member and actuated intoengagement therewith by said part when acted upon by currents of onepolarity to control the signal and telephone circuits, the contacts foreach station being arranged at a dilierent distance from r the neutralornormal position of the memher, a retaining device for the memberadapted to be released by the movement of said movable part whenenergized by a current of opposite polarity.

The combination with a main circuit, and a plurality of stations each,having a local telephone circuit and a local signal circuit, of aplurality of selecting devices one for each station embodying aprogressively movable member, actuated step by step by separate electricimpulses in the main circuit and connecting the local circuits of eachstation successively with the main circuit, a switch for opening themain circuit, a shunt leading around the switch and means locatedtherein for controlling the operation of the selecting device.

8. The combination with a main circuit, a generator and a telephonecircuit, of a selecting device embodying a movable member arranged inthe telephone circuit and adapted to be operated by electric impulses inthe main circuit and a resistance device arranged in the main circuitand adapted to prevent the operation of the selecting device withoutdestroying the telephone circuit.

9. In a signaling device, the combination with a stationary circuitcontact, a movable circuit contact, pawl and ratchet mechanism foroperating the movable contact progressively into engagement with thestationary contact, and a retaining device for said movable contact, ofa polarized electromagnet having apart engaging the pawl and ratchetmechanism when the magnetis energized by currents of one polarity, saidmagnet operating in a difierent direction to release the retainingdevice when energized by currents of opposite polarity.

10. The combination with a main circuit and a plurality of stationshaving local circuits ada ted to be connected to the main circuit, orselecting devices at each station embodying a polarlzed armature and arelatively movable electromagnet coil included in the main circuit,local circuit contacts, a progressively movable member, an arm operatedby the successive movements of the coil in one direction relatively toits armature to adjust the member step by step into engagement with saidcontacts, a retaining device for the member actuated to release it bythe movement of the coil in a difierent direction relatively to itsarmature.

11. The combination with a main circuit, a direct current generator, apole changer, and a plurality of subcircuits normally connected to themain circuit, of a selector for each sub-circuit having a movable armforming one terminal of said circuit, a contact point forming the otherterminal, said con tact points in the several selectors being arrangedin series, and electromagnetic devices in the several selectorsconnected to the main circuit movablein one direction toengage the armofeach selector and actuate it a single step for each electrical impulseof one polarity in the niaincircuit and move it into engagement with thecontact point,

said device operating in a-difierent direction to return the arm to itsnormal position by a single electrical impulse of opposite polarity inthe circuit.

12. The combination with a main circuit composed of two conductors, agenerator, and a series of local stations and telephone instrumentcircuits connected to the main circuit conductors, of a selecting devicefor each instrument circuit having contacts for their respectiveinstrument circuits, an operating device for each selector controlled bya current on the main circuit conductors, movable arms simultaneouslyactuated by. said devices for closing the instrument circuit contactsand means at each local station to control the flow of current from themain circuit to prevent the movement of the opcrating devices of theselector without deand forming the other terminal of said circuit, anelectro-magnetic operatingmecham ism connected to the main circuitconductors for actuating the arm and a switch arranged between the maincircuit and said operating device for controlling the operation of thelatter.

14. In a multiple telephone system, the

combination with a main circuit composed of two conductors, a generator,and a plurality of local circuits, adapted to be connected to the maincircuit conductors, of a selecting device arranged in each instrumentcircuit having a home contact and a separate instrument contactconnected thereto and forming dual terminals for one end of theinstrument circuit, a movable switch arm forming the other terminal ofsaid circuit and normally engaging the home contactpoint,electro-magnetic devices for operating the arm having a polarizedarmature and connected to the main circuit and operated by a currentthereon to move the arm into engagement with the instrument contact andmeans for regulating the operating device by controlling the currentflowing from the 'main circuit, without disconnecting the instrumentcircuittherefrom.

15. In a multiple telephone system, the

combination with a main circuit, a generator, and a plurality of localtelephone instrument circuits connected to the main circuit, of aselector arranged in each local circuit having a home contact point anda separate instrument contact connected thereto said contact pointsforming dual terminals for one end of the local circuit, a movablecontact member normally engaging the home contact, and operating devicesfor the member connected to the mam circuit and actuated by a currenttherein to move the member nito engagement with the instrument contact,a switch controlling the circuit to said operating device, and aresistance in shunt around the switch whereby the operation of thesclector'may be prevented without disconnecting the telephone instrumentcircuit during theactuating ofthe operating devices of the selectors ofthe remaining iiistruments.

16'. The combination with a main circuit and an instrument circuit, of aselecting deout-he operating device to move the switch arm intoengagement with the contact, when said device is moved in one directionand to I be disengaged from the arm when the de-' vice is'moved in adifferent direction, a retaining device operated by sald electromagneticdevice when responding to the impulses of current on the main-circuitdiflering in.

polarity from those actuating the switch 17. The combination with a mainelectrical circuit, an instrument circuit, and a selecting device havinga contact point form'- ing one terminal of the instrument circuit,"

a switch arm forming the other terminal and a 'pawl operating the arminto engagement with said contact, of an electro-magnetic devicecomprising a movable coil con nected to the main circuit adapted tobeopci'ated in one direction to operate the pawl loo and cause theswitch arm to be actuated rel atively to'the contact point and alsoadapted to disengage the pawl when moved in the V opposite direction, alocking device holding said arm in adjusted position, means operated bythe coil to disengage said locking device and permit the arm to bedisengaged from the contact. 7 18. The combination with a main electriccircuit, and an instrument circuit, of a,

selecting device having a contact point form ing one terminal of theinstrument circuit,

a signaling device adapted to be placed in naling and instrumentcircuits, an operating device in the main circuit actuating the arm,

a switch in the operating and the instru ment circuits.- and a condenserbrldg ng the switch.

19. The combination with a main circuit. and an instrument circuit, of aselecting device having a contact forming one terminal of the instrumentcircuit, a switch arm forming the other terminal, and a movableelectro-magnetic device in the main circuit having a polarized armatureand controlled by a current thereon, a pawl carried by said device andcooperating with the arm for moving the latter into engagement with thecontactwhen the device is operated in one direction by currents of onepolarity, a retaining mechanism for the arm, and means for disengagingthe latter operated by said magnetic device when moved in a difierentdirection by currents of diiferent polarity.

20. The combination with a main circuit and a continuous currentgenerator adapted to be connected thereto and a local circuit connectedto the main circuit, of a selecting device having a contact pointforming one terminal of the local circuit, a movable contact adapted toengage the first and forming the other terminal of said circuit, andpivoted electro-magnet coils having a stationary polarized armature andarranged in the main circuit and swung in opposite directions by currentof opposite polarity, an arm cooperating with the movable contact andoperated by the movement of the coils to close the local circuit whensaid coils swing in one direction and to disconnect said circuitterminals when the coils'swing in the other direction.

21. The combination with a main circuit, a generator therein, a localcircuit having two terminals and a movable contact cooperating therewithfor closing said circuits, either in normal or selected position, ofelectromagnet coils arranged in the main circuit and suspended from apivoted support, a relatively stationary polarized armature for thecoils and an arm operated by the swinging movement of the coils foradvancing the movable contact from the normal to the selected position.

22. The combination with a main circuit, a continuous current generatorand a local circuit, of a selecting device having a contact forming oneterminal of the local circuit, a movable contact arm forming the otherterminal for said circuit, teeth carried by the arm, an electro-magnetin the main circuit comprising pivoted coils and a relatively stationarypolarized armature and an actuating finger engaging the teeth to movethe arm one step relatively to the contact point for each movement ofthe coils in one direction, a pivoted retaining member normally engagingthe teeth and provided with a tripping finger operated by the movementof the coils in the opposite direction to dis engage said lockingmember.

23. The combination with a main circuit, a generator, a local circuitconnected thereto and a selecting device having a contact forming oneterminal of the local circuit, a movable contact arm forming the otherterminal for said circuit and teeth carried by the arm, of anelectro-magnet in the main circuit comprising pivoted coils and arelatively stationary polarized armature, an ac tuating finger carriedby the coils and engaging the teeth to move the arm one step relativelyto the contact point for each movement of the coils in one direction, apivoted retaining member engaging the teeth and a tripping fingeroperated by the movement of the coils in the opposite direction torelease the arm when the actuating finger is moved out of engagementwith the teeth. 24. The combination with a main circuit, a generator, alocal circuit connected to the main circuit, a selecting device having acontact point forming one terminal of the local circuit, and a movablecontact arm,- of a pivoted polarized magnet connected to the arm toactuate the latter relative the con tact point at each movement of themagnet in one direction, a locking member engaging the arm to retain itin ad]usted position, a tripping finger engaged. by the magnet whenmoved in the opposite direction, and a restraining device to preventexcessive movement of the magnet when returning to its normal positionafter its operation in either direction.

CHARLES E. NICHOLAS. lVitnesses:

C. WV. FAULKNER, THOMAS B. BLACK.

